You heard people talking about
Unertl's Tube sight------Take a look!

Our tube sight is used in conjunction with a full telescope height front
sight, properly raised so the front sight will appear well centered when sighted
in at 100 yards. For 50 or 200 yards, front sight will appear low or high, but
will be well within the field of the tube. The eye-piece end is threaded to fit
almost all standard sighting discs. The inside of the tube is properly
diaphragmed and from the eye-end another small steel inner tube extends into the
main tube to eliminate internal radiation and stray light. Our tube sight is
16" long and equipped with our latest type, precision 1/4 minute, target
type mount.